novel approaches to expression and detection of oestrus in dairy cows

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Viable sperm for 24-30 hours Optimal time to inseminate after oestrus, 4-12 hours Viable ova for 6- 12 hours Oestrus Ovulation 0 12 24 32 36 Hours after onset of oestrus Figure 1.2 Window of opportunity for artificial insemination post oestrus. The window of opportunity for AI in order to maximise conception rates. Sperm undergo capacitation and development in the female reproductive tract and are viable for 24-30 hours post insemination, therefore insemination must occur at 4-12 hours post onset of oestrus in order to coincide with ovulation around 28-32 hours post oestrus, and reach the ova which remains fertile for a short time, 6-12 hours, post ovulation. 1.2.2.3 Oestrous Synchronisation Oestrus can be synchronized and controlled by administration of exogenous hormones by precisely controlling the CL lifespan and follicular waves (Wiltbank et al., 1971;Thatcher et al., 1989;Pursley et al., 1995). This aids reproductive efficiency by controlling the oestrous cycle, acting as an aid to detection of oestrus. Exogenous oestrogens were found to control luteolysis in the early part of the oestrous cycle, but the onset of oestrus was not precise, although pregnancy rates were increased, compared with using progestagens (Wiltbank et al., 1971). Use of exogenous oestrogens is however now banned in the EU. However, luteolysis can be controlled by use of PGF 2α since its discovery as a luteolytic agent, or one of its synthetic analogues (Lauderdale et al., 1974). 5 days after injection of PGF 2α immediate regression of the CL occurs. The concentration of progesterone rapidly drops to basal levels within 24 hours, which allows LH pulse frequency to increase, causing significant increases in oestradiol concentration. Oestrous behaviour then occurs followed shortly by ovulation. However, CL regression is not always immediate depending on the stage of the follicular wave and the interval to onset of oestrus can be quite variable. If a dominant follicle is present then the onset of oestrus 12
can occur within 2-3 days, but if there is no dominant follicle this could take longer (Diskin et al., 2002). Conception rates in heifers undergoing synchronisation treatment and in heifers inseminated at natural oestrus have been reported to be unimpaired by treatment with no difference between the two groups (Macmillan and Day, 1982). However conception rates in lactating dairy cows can differ. Some workers reporting lower conception rates in cows inseminated at natural oestrus (Macmillan and Day, 1982) while others reported higher conception rate at detected oestrus compared to synchronized cows (Xu and Burton, 2000). Furthermore, pregnancy rate was often greater in cows synchronised due to increased detection and submission rates (Xu and Burton, 2000;Ryan et al., 1995). Emergence of new follicular waves can be controlled by exogenous GnRH administration to initiate a new follicular wave which aids the synchronisation of oestrous cycles. GnRH administration will cause ovulation if a dominant follicle is present and a new follicular wave will occur within 3-4 days (Webb et al., 1992;Twagiramungu et al., 1995). GnRH analogues have been implemented into a follicular and luteal phase synchronisation treatment, entitled the Ovsynch protocol, which controls emerging follicle waves and CL regression (Thatcher et al., 1989). This protocol uses timed injections; GnRH administered on day 0 results in ovulation followed by the initiation of a new follicular wave. PGF 2α treatment is administered 7 days later causing CL luteolysis, with a second GnRH dose 36-48 hours later inducing ovulation. AI is then carried out at a fixed time (Pursley et al., 1995;Stevenson et al., 1999b;Stevenson et al., 1999a;Thatcher et al., 1989). This protocol is advantageous because fixed timed AI eliminates the need for heat detection, which is cost effective, but heat detection is required if the first insemination fails (Diskin et al., 2002). However, as indicated previously with luteolytic inducing agents, GnRH + PGF 2α methods of synchronization do not increase conception rates when compared to AI at observed oestrus (Stevenson et al., 1999a). The Ovsynch protocol can also be accompanied by the ‘Presynch’ protocol involving two injections of PGF 2α 14 days apart followed by commencement of the Ovysnch protocol 14 days after the second PGF 2α injection (Akoz et al., 2008). Another variation on the Ovsynch protocol is Heatsynch; substituting the final GnRH injection 48 hours after PGF 2α treatment with an injection of oestradiol cyprionate intramuscularly at 24 hours after PGF 2α 13
Page 1 and 2: NOVEL APPROACHES TO EXPRESSION AND
Page 3 and 4: TABLE OF CONTENTS TABLE OF CONTENTS
Page 5 and 6: 2.2.3 Statistical Analyses ........
Page 7 and 8: 5.3 RESULTS .......................
Page 9 and 10: Furthermore, automated software was
Page 11 and 12: LIST OF FIGURES Figure 1.1 Hormonal
Page 13 and 14: LIST OF TABLES Table 1.1 Trends in
Page 15 and 16: LIST OF ABBREVIATIONS ˚ ˚C μM 2D
Page 17 and 18: CHAPTER 1 - Introduction & Literatu
Page 19 and 20: the past 50 years and duration of o
Page 21 and 22: Oestrus growing follicle (Staigmill
Page 23 and 24: ecomes the main inhibitor of FSH an
Page 25 and 26: calf at 40-50 days post partum; inv
Page 27: al., 2006). However, aged sperm hav
Page 31 and 32: educes the incidence of problem cow
Page 33 and 34: oestradiol, the LH surge and ovulat
Page 35 and 36: The secondary signs of oestrus can
Page 37 and 38: There are also changes in normal be
Page 39 and 40: engage in more natural behaviours i
Page 41 and 42: 1983). Exact explanations and mecha
Page 43 and 44: 2006) and disruption of LH secretio
Page 45 and 46: 1.4.3.2 Milk Yield and Nutrition Di
Page 47 and 48: influence the ability of the ovary
Page 49 and 50: cyclicity can be delayed if dietary
Page 51 and 52: indication for the optimal time to
Page 53 and 54: calving), 3) pre-breeding heat date
Page 55 and 56: 1.5.2 Physiological Changes Physiol
Page 57 and 58: 1.5.2.3 Body and Milk Temperature T
Page 59 and 60: physical activity and stage of the
Page 61 and 62: caused by the general environment t
Page 63 and 64: may be gained. This is because data
Page 65 and 66: In summary the objective was to for
Page 67 and 68: diet, with concentrates at milking.
Page 69 and 70: oestrus was defined as 3 consecutiv
Page 71 and 72: The interaction between parity and
Page 73 and 74: individual oestrus was not signific
Page 75 and 76: Table 2.4 The effects of the intera
Page 77 and 78: (361 vs. 578 points, respectively,
Page 79 and 80:
oestrous expression with increasing
Page 81 and 82:
the blood (Sangsritavong et al., 20
Page 83 and 84:
CHAPTER 3 - Single Nucleotide Polym
Page 85 and 86:
population owing to previous select
Page 87 and 88:
Table 3.1 Cont. Follicle Stimulatin
Page 89 and 90:
3.2.4 Sequencing of DNA in the Labo
Page 91 and 92:
was achieved. PCR products were rem
Page 93 and 94:
3.4 DISCUSSION The objectives of th
Page 95 and 96:
fertility and oestrous expression.
Page 97 and 98:
CHAPTER 4 - Development of a Novel
Page 99 and 100:
In summary UWB seems a good option
Page 101 and 102:
Initial tests were carried out to i
Page 103 and 104:
Therefore this demonstrates that X
Page 105 and 106:
which is most important for achievi
Page 107 and 108:
Figure 4.9 Horizontal - Vertical Di
Page 109 and 110:
that UWB is matching the ‘truth
Page 111 and 112:
mounting cow. For example height ch
Page 113 and 114:
Backpack 1 st put on in AI stalls E
Page 115 and 116:
Cows’ behaviour was assessed at 5
Page 117 and 118:
or that the cows were in an area of
Page 119 and 120:
plane, but mostly in achieving high
Page 121 and 122:
Develop techniques for analysis of
Page 123 and 124:
in elastic silicone moulded over a
Page 125 and 126:
and time of mount, duration of moun
Page 127 and 128:
observed matched with increases in
Page 129 and 130:
5.3 RESULTS Results demonstrate pos
Page 131 and 132:
Figure 5.2 Graph showing mounting b
Page 133 and 134:
Table 5.1 Results from POC 2 showin
Page 135 and 136:
Table 5.3 Efficiency and accuracy o
Page 137 and 138:
oestrus and oestrus it is clear to
Page 139 and 140:
P4 Concentration, ng/ml P4 Concentr
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Activity Activity Activity Activity
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
5.4 DISCUSSION The aim of this work
Page 155 and 156:
averaged 70% which was lower than t
Page 157 and 158:
when the cows lie down, especially
Page 159 and 160:
the level of oestrous activity was
Page 161 and 162:
technology larger herds must be mon
Page 163 and 164:
monitoring could also monitor non-l
Page 165 and 166:
antennae which could affect accurac
Page 167 and 168:
predispose cows to illness e.g. met
Page 169 and 170:
CHAPTER 6 - Overall Discussion & Co
Page 171 and 172:
oestrus, h 2 =0.27 (Lovendahl et al
Page 173 and 174:
The final section of this thesis de
Page 175 and 176:
ate. By using UWB in a commercial s
Page 177 and 178:
provides an insight the potential o
Page 179 and 180:
BLOWEY, R. (2005) Factors associate
Page 181 and 182:
ovine gonadotrophin releasing hormo
Page 183 and 184:
GINTHER, O. J., KOT, K., KULICK, L.
Page 185 and 186:
associated with embryonic survival
Page 187 and 188:
ody condition at parturition on end
Page 189 and 190:
Signs in a 24-h Tie-Stalled Dairy H
Page 191 and 192:
SHERMAN, E. L., NKRUMAH, J. D., MUR
Page 193 and 194:
Influence of negative energy balanc
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